Why North Africa went from green to desert in ancient times - FAST

Scientists studying North Africa's ancient climate have learned that the region underwent swift desertification and climate shift transforming from a humid, subtropical landscape to desert sands within a matter of years.

LOS ANGELES, CA (Catholic Online) - About 13,000 years ago, the Sahara went from a dry desert like it is today, to a relatively wet region watered by monsoons. Between 8000 B.C. to 4200 B.C., the region enjoyed a tropical climate. Civilization took root in Egypt during this period.

At that time, many tropical animals are believed to have existed in the region as evidenced by period artwork and natural remains.

However, around 4200 B.C. the climate became suddenly dry once again. The causes of this prehistoric climate change have been traced to the planet's axial tilt and a perihelion that occurred in July. This is distinct from modern climate change which may be caused by human activity and pollution.

Researchers have confirmed their conclusions with cores drilled from the bottom of the Atlantic Ocean where winds deposit massive amounts of Saharan dust each year. Scientists observed substantial increases in Saharan dust in layers dated between 6000 B.C. and 4200 B.C.

Those concentrations of dust are evidence that the Sahara became much drier and turned to desert during that period, correlated with changes in the Earth's tilt. Notably, the levels of dust in the cores are about 20 percent of what they are today, suggesting that the Sahara has since become as much as five times drier than it was then.

It is believed that in addition to changes in the planet's orientation, melting ice caps, from the end of the last ice age, contributed to the wetter weather, and that once those ice caps shrank sufficiently, they no longer impacted tropical climate enough to keep the North Africa wet.

Today, as the ice caps melt more than at any point in recorded history, the desert is drier than ever before.

Ironically, snow fell in parts of Algeria on January 18, 2012. Despite this bizarre event, the weather remains much drier than at any time in history. The Sahara is also growing, consuming farm and ranch land across the Sahel region to the south.

Researchers are still trying to determine what impact the Sahara had on ancient climate, however they are certain of one thing. Climate change, whatever its cause, it often sudden and substantial. It can make deserts of jungles and jungles of deserts, and in the modern era such shifts could bring disaster.

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